With a shark and two of these bad boys as an escort, the ocean is your oyster. Mine have protected me flawlessly against sharks, anglers, eels, and manta with their sweeping stun attack. Even Plesiosaur and Mosa get quickly overwhelmed by the sheer DPS two of these can do as it will alternate who it attacks rather than focusing on one Dino. I’ve even been saved from JELLYFISH by these guys as they can attack in any direction even when being stunned (a swarm of jellies will stun lock them, but one or two is manageable with enough melee and HP boost.)
WARNING you can easily lose this Dino in the ocean after fighting manta and Megalodon as each shark gives them 300 or so fish meat and mantas around 200 - they get overburdened with meat FAST. Check their weight after each big fight!!
Baryonyx are quick like Allosaurus and do just as much damage (but don't get a pack bonus). They don't use oxygen for swimming and can sprint in the water. Right click in the water does an AoE stun that lasts about 10 sec. Their 'C' is a... Taunt? They also jump and you can fire a weapon from their back.
It's like a small Allo combined with a Kapro, in my opinion. Useful on both land & in the water. Use its secondary attack while swimming to stun, attack, and harvest. Does NOT stun Cnidarias, though, so do not expect to overpower them.